1. Field of the Invention
This invention relates to a photosensitive resin composition for forming electrically conductive patterns and to a method for using the photosensitive resin composition to form such patterns.
The conductive patterns formed by the invention are used as printed circuits, electrodes, heating elements and the like.
2. Description of the Background Art
Typical of the conventional methods for forming conductive patterns are (1) the pattern printing process using conductive paste, (2) the subtractive process in which the conductive pattern is formed by etching a copper-plated laminate to remove nonpattern regions, and (3) the additive process in which a plating resist pattern (negative) is formed on a substrate and the remaining portions are selectively plated.
Among the shortcomings of method (1) are that the conductivity of the pattern, the adhesive strength of the paste and the pattern precision are low while the production cost is high. As relates to application of the method in the printed circuit field, moreover, it is not practical from the point of through-hole continuity and the fact that the paste exhibits low soldering heat resistance.
Method (2) has problems in that the process is complex, fine pattern features are difficult to form and the plating adhesion at through-hole portions is less than satisfactory. What is more, the method has already matured to the point where further substantial improvements cannot be expected.
Method (3) was developed to eliminate waste arising from the removal of nonpattern portions by etching and to respond to demands for higher wiring density and reliability. However, since the catalyst-containing resin layer that the plating is applied to is not patterned, its electrical insulation property is poor. Further, the method does not enable easy formation of fine patterns, the catalyst contained in the substrate further impairs the insulation property, the strength and other physical properties are inferior, the cost of catalyst is high, the plating adherence is low, and roughening is required prior to plating.